Compression method and means

ABSTRACT

The invention is a compression method having characteristics of smooth compression and internal cooling of the gas. Embodiments of the invention employ a cylindrical chamber and an orbiting rotor to create a moving duct or chamber whose walls converge, relative to a static gas packet drawn into the moving duct, at a ‘pinch point’. Preferably the closing speed of the walls is subsonic and the speed of the pinch point is supersonic. This enables high pressure to co-exist, at the narrowing end of the duct, with low pressure elsewhere in the duct, because of the pressure information barrier produced by the supersonic advance of the pinch point. The invention also discloses means for adjusting the running clearance between the cylinder and the rotor, and means for counterbalancing the rotor.

This application relates to the field of gas pumping and compression.

BACKGROUND OF THE INVENTION

Gas compression devices used in refrigeration, air conditioning andindustry consume a large portion of electrical power generated. Anincrease in gas pumping efficiency will result in reduction of carbondioxide emissions. Proposals to sequester carbon dioxide at pressureunderground or in the ocean depths are dependent on using compressionmethods that are efficient and can also overcome problems such as phasechange and the material erosion of compressor parts when compressingimpure gas mixture. Small changes in compressor efficiency may determinewhether carbon sequestration is commercially viable.

Efficient compression requires that as little kinetic energy as possibleis imparted to the gas molecules. This implies that a gas packet shouldmove as slowly as possible through the compressor, without suddenaccelerations. The direction of motion should preferably be in astraight line. There should be no sudden changes of volume that mightlead to shock formation at high speeds. Since gas noise is initiated bythe kinetic energy of the gas, a compressor that compresses smoothly andgently will be quiet in operation.

Heat of compression spreading back by leakage or thermal conductance tothe intake gas or to less compressed gas in the compression chamber is acause of inefficiency in compressors requiring additional work energyequal to any increased heat acquired by the gas both before entering andwithin the compressor. Some of the heat of compression flows into thewalls of the compressor. Because this heat cannot be removed quicklyenough, the walls remain hot, heat remains in the gas and the workrequired rises. It is desirable, therefore, that as gas is compressedand heated some or all of the heat of compression should be removed fromthe gas as it moves through the compressor. Conventionally this is doneby cooling the compressor walls or by water injection. However in pistonand cylinder compressors the gas is compressed into a volume defined byunchanging but decreasing surface, therefore there is little possibilityof removing the heat of compression during the process. The higher therise the greater is the loss of efficiency.

Known types of compressors typically suffer from problems which tend toreduce efficiency, including but not limited to those described herein,namely:

-   -   impartation of large amounts of kinetic energy to the gas being        compressed    -   sudden acceleration of gas leading to high noise levels and        energy losses    -   high gas flow speeds leading to frictional heating of the gas        being compressed, leading to an increased work requirement    -   heat of compression feeding back to the intake charge, leading        to an increased work requirement    -   variable internal surface area leading to a reduced ability to        remove heat of compression from the gas being compressed    -   high rubbing speeds between internal components leading to wear        and frictional losses    -   low inter-stage compression rise    -   large physical size relative to gas processing rate

BRIEF DESCRIPTION OF INVENTION

The invention is set out in the claims.

In an embodiment of the invention there is provided a compressorcomprising a cylinder and a rotor, whereby the rotor traverses theinternal circumference of the cylinder and a pinch point is formed atthe closest point of the rotor periphery to the internal wall of thecylinder. The rotor traverses the internal circumference of the cylindersuch that the pinch point moves at high, preferably supersonic speed. Inan embodiment, the rotor rolls around the internal circumference of thecylinder such that the speed of the rotor surface, relative to thecylinder wall, is low or zero, thus reducing wear and frictional heatingof the components and of the gas to be compressed, termed herein“rolling”, thus aiding compressor efficiency. Optionally, a strip valvearrangement on the rotor surface allows entry of gas into the chamberformed between rotor and cylinder. Optionally, a strip valve arrangementon the cylinder wall allows exit of gas from the chamber and optionallyincorporates actuation means to control its opening position.

In another embodiment of the invention there is provided a compressorcomprising a cylinder and a rotor, whereby the rotor traverses theinternal circumference of the cylinder and a pinch point is formed atthe closest point of the rotor periphery to the internal wall of thecylinder. The rotor moves such that the pinch point moves at high,preferably supersonic speed. The rotor rotates around the internalcircumference of the cylinder such that a fixed point on the rotorperiphery is maintained adjacent to the pinch point—termed herein“rotating”. Optionally, ports in the rotor allow entry and exit of gasvia passages communicating with the axial ends of the cylinder.

In a further embodiment, the rotor orbits around the cylinder such thatthere is no rotation of the rotor itself—termed herein “orbiting”.

Embodiments of the invention incorporate valve means for allowingcompressed gas into the chamber and for allowing compressed gas out ofthe chamber.

Embodiments of the invention incorporate an arrangement for adjustingthe running clearance between the rotor surface and the innercircumference of the cylinder.

Embodiments of the invention incorporate an arrangement forcounterbalancing the rotating mass of the rotor and associated rotatingparts. Such counterbalancing means can optionally be adjustable.

Embodiments of the invention incorporate rotor surface features in orderto increase compressor efficiency.

Embodiments of the invention will now be described, by way of example,with reference to the figures which are as follows:

FIG. 1—Schematic view of compressor housing and rotor

FIGS. 2 a to 2 g—‘Rolling’ rotor operation

FIGS. 3 a to 3 g—‘Orbiting’ rotor operation

FIGS. 4 a to 4 g—‘Rotating’ rotor operation

FIG. 5—Strip valve arrangement

FIG. 6—Rotor port arrangement

FIG. 7—Rotor surface features

FIG. 8—Spiral duct embodiments

FIG. 9—Rotor balancing/drive arrangement

FIG. 10—Strip valve and balancing arrangement

FIG. 11—Strip valve actuation arrangement

DETAILED DESCRIPTION

As shown in FIG. 1, the present invention provides a compression methodthat has the desired characteristics of smooth compression and internalcooling of the gas. This method employs a cylindrical chamber (10) androtor or orbiter (20) to create a moving duct or chamber (40) ofunchanging geometry and size, whose walls converge relative to a staticgas packet drawn into the moving duct (40). The duct (40) walls convergeat a lower speed than the point of closest approach of the walls[hereinafter called the pinch point (50)] moves along the duct (40). Inpreferred operation the closing speed of the walls is subsonic and thespeed of the pinch point (50) is supersonic. As the pinch point (50)advances, the volume in which gas is at highest pressure/temperaturealso advances to areas of the walls that have been cooled since lastbeing adjacent to the high temperature gas. When such a compressor isoperating with the pinch point (50) moving at supersonic speeds,information about the pressure rise caused by narrowing of the duct (40)cannot propagate forward and push the gas forward. This enables highpressure to co-exist, at the narrowing end of the duct (40), with lowpressure elsewhere in the duct (40) because the volumes are physicallyseparated by the pinch point (50) and the pressure information barrier(40) produced by the supersonic advance of the pinch point (50). Thisprovides a compressor that has the high pressure ratio capability ofpositive displacement compressors combined with the smooth pulse-lessoutflow of centrifugal and axial machines.

The invention can be realised in various embodiments by employing a duct(40) created between an inner circumference of a cylinder (10) and ashaped wall (20) moving within the cylinder (10) so as to form anarrowing of the duct (40) at the point of closest approach of the twomembers (50).

Three embodiments demonstrating variations on the movement of the rotor(20) within the cylinder (10) will now be described.

As shown in FIGS. 2 a to 2 g, as can be used in a first class ofembodiments described below, a ‘rolling’ rotor (20) rolls around theinner circumference of the cylinder (10) as the rotor (20) traverses theinner circumference of the cylinder (10). The orientation of the rotor(20) is shown by respective arrows A, B, C in FIG. 2 a. The sequence ofsix illustrations shown consecutively in FIGS. 2 b to 2 g illustrates(see arrow A in each) how the orientation of the rotor (20) changes withrespect to the cylinder (10) as the rotor (20) rolls around the innercircumference of the cylinder (10). The rotor changes orientation as itrolls such that the speed of the rotor (20) surface, relative to thesurface of the inner circumference of the cylinder (10) is substantiallylow or zero. The rotor (20) can be arranged to substantially contact theinner surface of the cylinder (10) or the two surfaces can be spacedslightly apart. The rotor (20) can be arranged to roll by means ofcontacting the inner surface of the cylinder (10) or can be rotated byother means such as gears or by entrainment by the gas being compressed.This feature results in a substantially low or zero rubbing speedbetween the surface of the rotor (20) and the inner surface of thecylinder (10), which in turn results in improved wear performance ofthose surfaces. Other results of this feature are lower frictionallosses, lower kinetic energy imparted to the gas being compressed (lowerentrainment) and lower frictional heat imparted to the gas beingcompressed. These results all contribute to greater efficiency of thecompressor.

As shown in FIGS. 3 a to 3 g, as can be used in the first class ofembodiments described below, an orbiting rotor (20) does not changeorientation with respect to the cylinder (10) as the rotor (20)traverses the internal circumference of the cylinder (10). FIG. 3 ashows sequential position 20 a, 20 b, 20 c and correspondingorientations with arrows A, B, C. FIGS. 3 b to 3 g show the sequentialrotor positions and corresponding orientation A. An orbiting rotor (20)results in a greater relative speed between the surface of the rotor(20) and the inner surface of the cylinder (10) than with the rollingrotor (20) of FIG. 2, but a lower relative speed than with a rotatingrotor (20) as will be described in the following paragraph. Efficiencylosses when an orbiting rotor (20) is employed tend therefore to be in arange between those of the rolling rotor (20) and those of the rotatingrotor (20).

As shown in FIGS. 4 a to 4 g, as can be used in the first class ofembodiments or a second class of embodiments described below, therotating rotor (20) changes orientation as the rotor (20) traverses theinternal circumference of the cylinder (10), in such a way that a fixedpoint on the rotor (20) surface A, B, C in the sequential positions 20a, 20 b, 20 c in FIG. 4 a is adjacent to the pinch point (50). Themovement of point A can be seen in the sequential position shown inFIGS. 4 b to 4 g. A rotating rotor (20) results in a greater relativespeed between the surface of the rotor (20) and the inner surface of thecylinder (10) than either the rolling rotor (20) of FIG. 2 or theorbiting rotor (20) of FIG. 3. Efficiency losses when a rotating rotor(20) is employed tend therefore to be in a range which is higher thanthose of the rolling rotor (20) of FIG. 2 or the orbiting rotor (20) ofFIG. 3. An advantage of the rotating rotor (20) of FIG. 4 is that agreater range of valve arrangements can be practically used than withthe other two rotor (20) types. A compressor incorporating the rotatingrotor (20) can be made with fewer moving parts than a compressorincorporating the other two types of rotor.

As shown in FIG. 5, in a first class of embodiments, the duct (40) is achamber formed between two cylinders, one relatively static (10) andacting as a stator and the other (20) acting as a rotor—rolling,orbiting or rotating it within it. Using a valving mechanism describedbelow, gas is drawn into the duct (40) by a rarefaction caused by thewidening of one end the duct (40) (i.e. when the rotor is adjacent anopposing side of the stator). It passes through inlets in the walls ofeither of the cylinders (10, 20) or of the end walls and is expelled athigher pressure at the other end of the duct (40) after it has beencompressed by a relative narrowing of the duct (40) caused by theorbiting component (20) approaching the stator wall. By mounting bladesinside the rotor (20), a degree of pre-compression can be achieved. Insuch an embodiment the rotor (20) may have a rolling or rotating surfaceor may orbit without rotation.

In a device built according to such a first class of embodiments, asshown in FIGS. 5 and 10, there is provided a cylindrical rotor (20),within a cylinder (10). The rotor (20) is provided with a surfacechannel (210), of depth equal to the thickness of strip (220) that fitswithin the channel (210). The strip (220) is of larger circumferencethan the rotor (20) circumference, so that when the strip (220) ispressed onto the rotor (20) it forms a gas tight seal. However becausethe strip (220) is of larger circumference than the rotor portion (20),the strip (220) will always protrude above the rotor (20) surfacecircumference, away from the final point by virtue of the squeezingforce exerted on it there, allowing gas to flow through openings (230)in the base of the channel (210) to outside the rotor (20).

The cylinder (10) is similarly provided with a channel (240) and strip(250) on the outside, allowing gas to pass from the inside of thecylinder (10) to ducting means on the outside. This outlet strip (250)may be provided with reinforcement across its width to support itagainst high gas pressures.

In operation the rotor (20) orbits, preferably at a speed that resultsin the pinch point (50) between the rotor (20) and cylinder (10)rotating at supersonic speed. As the pinch point (50) rotates, lowpressure follows behind (in terms of the direction of rotation) thepinch point (50), pulling the strip valve (220) away from the rotor (20)and continuously inducing gas into the chamber (40). At the other end ofthe chamber (40) the converging surfaces of rotor (20) and cylinder (10)compress previously inducted gas and force it out of the chamber (40)through the exit strip (250), which is forced to and held in an openposition by the pressure of gas in front of the pinch point (50). Toprevent the exit strip (250) overlapping the pinch point (50) andallowing gas to escape from the high pressure volume into the lowpressure volume, the exit strip (250) may be actuated by mechanical,electrical or magnetic means to control the distance of its opening(270) from the pinch point (50). As shown in FIG. 11, a cam (261) on thedrive shaft (660) operates a pushrod (260) which operates to lift theexit strip (250). This actuation is also helpful for controlling startand shutdown conditions and to give a degree of capacity control. Inrolling or rotating rotor embodiments (see below) where the highpressure exit side of the pinch point (50) can be separated by somedistance from the low pressure inlet side, actuation of the strip (250)may be used to restrict the area of the outlet by moving the opening(270) partially past the pinch point (50) and so controlling thepressure ratio of the device. Hence, in an embodiment, a strip isdeformable by mechanical actuation, in particular by an actuator such asa cam and pushrod coupled to the rotor, for example the rotor driveshaft.

As shown in FIG. 6, a blind passage (275) or passages are providedwithin the rotor, open on the axial face and terminating adjacent theinside of the rotor surface. This passage (275) communicates with theaxial face of the rotor (20), so that cooling fluid may be circulatedbehind the rotor (20) circumferential surface. The walls and end platesof the chamber (10) are additionally provided with passages for thecirculation of cooling fluid. Finned means (276) may be provided toincrease the heat flow from the chamber (10) walls to be cooled into thecooling fluid.

In operation the rotor (20) is rotated with the inlet conduit (330)leading, so that the duct (40) rotates with the rotor (20) at a speedpreferably in excess of the local speed of sound. Appropriate curvatureof the inlet conduit (330) passage way causes gas to be drawn from anaxial face of the rotor (20) into the conduit (330) in a substantiallyradial direction. As the duct (40)—i.e. the space between rotor andstator—rotates around the stator, the gas is confined to a convergingduct (40) formed between the surface of the rotor (20) and the cylinder(10) wall. The supersonic speed of the approaching pinch point (50) doesnot give time for information about increasing pressure to propagateupstream. The gas is steadily compressed until, as the pinch point (50)reaches the gas, it is permitted to escape at high pressure through theoutlet (340) and through passages within the rotor (20) to a radial endof the rotor (20) from whence it is ducted out of the device. Duringcompression in the duct (40) the gas temperature increases. The heat ofcompression is transferred continuously, both through the wall of therotor (20) into the cooling fluid circulating behind the wall andthrough the chamber walls (10) into the cooling fluid (277) circulatingthere.

As shown in FIG. 7 the surface of the rotor (20) may be provided withspiral grooves (400) and/or passages (410) to conduct high pressure gasthat passes the pinch point (50) or along the axial ends of the chamberback to a selected or controlled point (420) in the duct (40). This gasis cooled on its passage back to the chamber and this is moreadvantageous for the efficiency of the device than allowing it tore-emerge at the inlet end of the chamber (330). In complex devices itwould be possible to bleed this gas through micro pores (430) in therotor surface to promote laminar flow.

In this second class of embodiments the device may include a rotor (20)with the converging duct (40) formed between the cylinder (10) wall andthe surface of the rotor (20) (as shown in FIG. 6) or the convergingduct (40) may be formed between the cylinder wall (10) and a channel ofreducing cross-section (330) on the rotor (20) where the rotor isconcentric with the stator (as shown in FIG. 8).

Referring, for example, to FIGS. 7 and 8, as an aim of the invention isto avoid accelerating gas, it is important that for a givencross-section of duct (40) the ratio of stationary to moving duct (40)surfaces should be as high as possible. In embodiments using a channel(330) within the rotor (20), the duct (40) may be formed by a groove(580) which winds spirally down the circumferential face of the rotor(20) so that all parts of the duct (40) including the high pressure/hightemperature end of the duct (40) are continuously exposed to freshsurface areas to conduct heat from the duct (40). In such an embodimentheat transfer up the cylinder stationary wall (10) may be reduced byflanges (350) behind the surface (see FIG. 6). The rotor (20) may befurther cooled by internal fluid flow along the sides of the duct (40)and side of rotor (20).

As shown in FIG. 8, a second class of embodiments employ a rotatingrotor (20). In such a device there is provided a rotor (20) within acylinder (10), the rotor (20) being profiled so that a substantial partof the rotor (20) circumferential surface remains in rotatably closeproximity to the inner wall of the cylinder (10) as it traverses theinner wall. The remaining circumferential surface of the rotor (20) isshaped or cut out so as to create a duct or groove (40) with a narrowingend (530) between it and the cylinder (10) wall. A wider end of the duct(540) is provided with an inlet conduit (520) communicating with thecentral part of an axial face of the rotor (20). Spaced from the duct(40) the circumferential surface of the rotor (20) is provided with anexit conduit (550) communicating with another portion of the axial faceof the rotor (20). In large devices there may be provided more than oneshaped duct (40).

In a spiral duct (500) embodiment the output pressure ratio may becontrolled by providing a moveable sleeve (510) between the rotor (20)and cylinder (10). In operation, gas inlet (520) is through one axialend of the chamber (40) and outlet (550) through the other. Moving thesleeve (510) axially with respect to the rotor (20) changes the outletarea and so changes and controls the pressure ratio of the device.

Any of the above embodiments may be provided with means to adjust theoffset of the rotor (20) from the central axis of the containingcylinder (10) and so adjust the clearance between the rotor (20) andcylinder (10) at the pinch point (50). This is advantageous for wearcompensation, adjusting for different rates of thermal expansion,reducing leakage and to control capacity.

As shown in FIG. 9, an arrangement for driving the assembly, andadditionally adjusting the offset of the rotor (20) from the centralaxis of the containing cylinder (10), and thereby adjusting theclearance between the rotor (20) and the cylinder (10) at the pinchpoint (50), is described herein. In overview, the rotor (20) has a rotoraxis (670) each end of which is coupled to a drive rotor support and anidler rotor support (680, 690) respectively, each of the drive rotorsupport and the idler rotor support (680,690) in turn are coupled to adrive shaft and an idler shaft (660, 650) respectively, which arearranged such that they are on the central axis of the cylinder (10) andare each supported by a bearing support (630).

In more detail, an end of the rotor axis (670) is joined by a coupling(600) to a drive rotor support (680), and an other end of the rotor axis(670) is joined by a coupling (600) to an idler rotor support (690). Theidler rotor support (690) is joined by a coupling (600) to a fixed shaft(650). The drive rotor support (680) is joined by a coupling (600) to adrive shaft (660). Both drive shaft (660) and idler shaft (650) arearranged to be parallel to the rotor axis (670) and to lie on thecentral axis of the cylinder (10). Each rotor support (680, 690) isarranged to support the rotor axis (670) such that the rotor (20)surface is substantially positioned close to the inner circumference ofthe cylinder (10). Both idler shaft (650) and drive shaft (660) aresupported by a bearing support (630) and are rotatable within, andaxially constrained relative to said bearing support (630). Each bearingsupport (630) is arranged such that its axial distance from the centreof the rotor axis (670) is equal to that of the other bearing support(630) and is controllable. By controlling the distance of the bearingsupports from the centre of the rotor axis (670) it is possible to varythe position and angle of each rotor support (680, 690) and resultantlyit is possible to vary the running clearance between the rotor (20) andthe housing (10).

Three classes of coupling (600) can be advantageously employed in thepreceding arrangement. A first class of coupling (600) includescouplings which are suitable for forming a joint which is articulated intwo axes between two shafts, but not capable of transmitting any axialtorque. An example of a commonly known coupling (600) falling into thefirst class is a ball joint. A second class of coupling (600) includescouplings which are suitable for forming a joint which is articulated intwo axes between two shafts, and capable of transmitting axial torque.An example of a commonly known coupling (600) falling into the secondclass is a constant velocity joint, a Hardy-Spicer universal joint,certain types of rubber couplings or compliant rubber tubing. A thirdclass of coupling includes couplings witch are suitable for forming ajoint which is capable of articulating in one axis and capable oftransmitting axial torque. An example of such a joint is a hinged joint.

The drive shaft (660) can transmit rotational torque via a drivecoupling (640). The drive shaft (660) is coupled to the drive rotorsupport (680) by a coupling (600) of the third class. The end of thedrive rotor support (680) which is coupled to the rotor axis (670) isthereby constrained to orbit in a circular motion around the draft shaft(660) axis.

In embodiments employing a rolling rotor, the drive rotor support (680)is coupled to the rotor axis (670) by a coupling (600) of the firstclass. The rotor axis (670) is coupled to the idler rotor support (690)by a coupling of the first or second class. In such embodiments, eitherat least one of the coupling (600) which couples the rotor axis (670) tothe idler rotor support (690) and the coupling (600) which couples theidler rotor support (690) to the idler shaft (650) are of the firstclass, and/or the idler shaft (650) is free to rotate. The rotor (20) isthereby free to roll independently of the drive shaft (640) orientationand the idler shaft (650) orientation, but the rotor (20) is compelledto traverse the inner circumference of the cylinder (10) by the drivetransmitted from the drive shaft (640) to the drive rotor support (680).

In embodiments employing an orbiting rotor, the drive rotor support(680) is coupled to the rotor axis (670) by a coupling (600) of thefirst class. In such embodiments, both of the coupling (600) whichcouples the rotor axis (670) to the idler rotor support (690) and thecoupling (600) which couples the idler rotor support (690) to the idlershaft (650) are of the second class, and the idler shaft (650) is fixedso that it cannot rotate. The rotor (20) is thereby constrained so as tomaintain its orientation with respect to the cylinder (10) by virtue ofits connection to the fixed idler shaft (650). The rotor (20) iscompelled to traverse the inner circumference of the cylinder (10) bythe drive transmitted from the drive shaft (640) to the drive rotorsupport (680).

In embodiments employing a rotating rotor, the drive rotor support (680)is coupled to the rotor axis (670) by a coupling (600) of the second orthird class. The rotor axis (670) is coupled to the idler rotor support(690) by a coupling of the first or second class. In such embodiments,either at least one of the coupling (600) which couples the rotor axis(670) to the idler rotor support (690) and the coupling (600) whichcouples the idler rotor support (690) to the idler shaft (650) are ofthe first class, and/or the idler shaft (650) is free to rotate. Therotor (20) is thereby constrained to maintain its orientation withrespect to the drive rotor support (680), and is unconstrained relativeto the idler rotor support (690) orientation, and as a result, a fixedpoint on the rotor (20) surface is maintained adjacent to the pinchpoint (50). The rotor (20) is compelled to traverse the innercircumference of the cylinder (10) by the drive transmitted from thedrive shaft (640) to the drive rotor support (680).

Although the rolling, orbiting and rotating rotor constraintarrangements have been herein described with reference to the use ofspecific combinations of the aforementioned classes of coupling, it willbe appreciated that the rotor characteristics described herein can beaccomplished by other combinations not described. Accordingly, thedescriptions of the orbiting, fixed, and rotating rotor constraintarrangements described herein are not intended to be limiting to thescope of the invention, the invention being set out in the claims.

As shown in FIG. 9, a means for counterbalancing the rotor (20) isprovided. The drive rotor support (680) is extended past the coupling(600) which couples the drive rotor support (680) to the drive shaft(660), in a direction away from the rotor (20). A counterbalance weight(620) is provided either separately, or integrally with the drive rotorsupport (680) extension. Similarly, the idler rotor support (690) isextended past the coupling (600) which couples the idler rotor support(690) to the idler shaft (650), in a direction away from the rotor (20).A counterbalance weight (620) is provided either separately, orintegrally with the idler rotor support (690) extension. Eachcounterbalance weight (620) is arranged to have a weight and a distancefrom the central axis of the cylinder (10) such that the weight of therotating components on the opposite side of the central axis of thecylinder (10) is balanced. The mass or position of the counterbalanceweights (620) can be adjusted during operation of the compressor, tocompensate for thermal expansion or other effects which would otherwiseupset the balance of the rotating components of the compressor. This canbe achieved by the use of actuators to adjust the position of thecounterbalance weights (620) on the rotor supports (680, 690),Alternatively, the mass of the counterbalance weights (620) can bealtered, for example by pumping fluid or gas in or out of thecounterbalance weights (620) which can incorporate a fluid or gasreservoir.

FIG. 10 shows an alternative arrangement for counterbalancing the rotor(20) where the drive shaft (660), rotor axis (670) and counterbalanceweights (620) are housed within the cylinder (10), this beingadvantageous in that sealing of the chamber is facilitated.

Although the manner in which the various chambers are sealed and ductedare not described in all cases in detail it will be appreciated that inembodiments of this invention the usual sliding seal means of thecompressor art are provided to prevent leakage of gas from high pressurevolumes to low pressure volumes. Ducting means to direct low pressuregas into devices and high pressure gas away from the device are alsoprovided.

In any of the above embodiments conventional control means of the art,such as valves, may be used in combination to control and regulate flow.

Although embodiments have been described with a static cylinder (10) anda movable rotor (20), other embodiments may employ a moving cylinder(10) and static rotor (20) or both moving rotor (20) and cylinder (10).

A compressor constructed according to this invention may be reversed,with appropriate valving, to operate as an expander.

Advantages of the present invention are that high efficiency ofcompression and high stage pressure rise are achieved by compressing gaswhile imparting as little kinetic and friction energy to the gas. Theinvention also allows cooling of the gas while it is being compressed.

In axial and centrifugal compressors the necessity of multiple stages,caused by the low pressure rise per stage can be exploited to provideinter-cooling between stages. For high efficiency of compression allsurfaces enclosing the gas may be cooled and the gas and/or surfacescontinuously changed so that the gas is brought into contact withfreshly cooled surfaces during compression. Preferably the gas shouldnot flow relative to the walls as this causes frictional heating.

The invention has several advantages over prior art compressors. Theseinclude:

By employing supersonic rotation of the pinch point, the simplemechanical layout of the invention is made possible, since high pressurecannot propagate to the low pressure areas of the chamber and thereforeno mechanical separation between low and high pressure regions of thechamber is required.

The continuous rotational compression means of the invention allows forsmooth continuous compression. By employing smooth and continuouscompression means, the invention advantageously reduces the energyimparted to the gas being compressed.

By employing adjustable running clearance means, and/or a rotor whichrolls as it traverses the internal circumference of the cylinder,frictional losses are reduced, which reduces heating of the gas to becompressed and thereby increases efficiency.

The fixed chamber volume of the invention allows for enhanced heattransfer properties because the maximum chamber surface area is alwaysin contact with the gas being compressed. This allows the gas beingcompressed to be more effectively cooled, which in turn aids compressorefficiency.

The amount of gas processed in each revolution is greater than thevolume of the interior volume of the cylindrical chamber and the volumeof the rotor. The swept volume is the cylinder volume less the volume ofa rotor having a radius equal to: {radius of the rotor minus the radialoffset of the rotor axis from the cylinder axis}. In other words, thesweep path of the rotor surface diametrically opposite the pinch pointdefines the swept volume.

A further advantage of the present invention is that it exhibits highflow properties compared to, for example, axial or centrifugalcompressors of a similar physical size. As a result, the compressor ofthe present invention can be made physically smaller than knowncompressors.

Although the invention has been explained in relation to its preferredembodiments, these are not intended to limit the invention. It will beunderstood by those skilled in the art that many other modifications andvariations are possible without departing from the scope of theinvention as claimed. Embodiments and features of embodiments may bejuxtaposed or interchanged as appropriate.

1. A gas compressor comprising: a rotor and a stator, one of the rotorand stator having a closed internal surface for relative traversal withrespect to the other to form a pinch point at a point of nearestproximity; and a compressed gas outlet.
 2. The gas compressor accordingto claim 1 in which the pinch point is arranged to move at substantiallysupersonic velocity.
 3. The gas compressor according to claim 1 whereinin use a fixed point on the rotor surface is substantially maintained atthe pinch point.
 4. The gas compressor according to claim 1 wherein inuse the rotor orientation substantially does not change with respect tothe stator.
 5. The gas compressor according to claim 1 wherein in usethe rotor rolls around the stator surface such that the rotor surfacedoes not rub against the stator surface.
 6. The gas compressor accordingto claim 1 wherein the rotor and/or stator incorporates a coolingpassage.
 7. The gas compressor according to claim 1 wherein the rotorand/or stator incorporates cooling fins.
 8. The gas compressor accordingto claim 1 wherein the rotor incorporates said outlet.
 9. The gascompressor according to claim 1 wherein the outlet is positioned at therotor or stator upstream, in the traversal direction of the pinch point.10. The gas compressor according to claim 1 wherein the statorincorporates said outlet.
 11. The gas compressor according to claim 1wherein the rotor incorporates an inlet for uncompressed gas, downstreamin the traversal direction of the pinch point.
 12. The gas compressoraccording to claim 1 wherein at least one of a gas inlet and said outletcomprises an orifice on a traversal surface of at least one of thestator and rotor.
 13. The gas compressor according to claim 1 in whichat least one of a gas inlet and said outlet comprises a circumferentialstrip deformable away from said orifice at least one gas inlet or outletto allow gas flow therethrough.
 14. The gas compressor according toclaim 1 wherein at least one of a gas inlet or said outlet comprises aduct opening at a circumferential surface of the rotor.
 15. The gascompressor according to claim 1 wherein the rotor is supported to allowvariable proximity to the stator at the pinch point.
 16. A valvearrangement comprising: a body having an outer wall housing a valveorifice; and a circumferential deformable strip arranged around thehousing so as to close the orifice in an undeformed state and deformableto open the orifice to allow gas flow.
 17. A method of compressing gascomprising: causing relative traversal of a rotor and a closed internalstator surface with respect to each other to form a pinch pointtherebetween, at the point of nearest proximity, in which the pinchpoint moves at a substantially supersonic speed.
 18. The method asclaimed in claim 17 in which the rotor is supported to allow variableproximity to the stator at the pinch point.
 19. A gas compressorcomprising: first and second elements, at least one of said first andsecond elements being capable of relative rotational movement withrespect to the other to form a pinch point arranged to compress gas at apoint of nearest proximity.
 20. (canceled)